It would be nice if the physical placement of the small squares that represents cards on the timeline, would reflect the actual due date of the card. That way you have a visual clue as to when next card activity will occur and when activities was completed prior to today. Also you could place in a special area and/or colorcode cards without due dates and cards with due dates outside the timeline of the activity to which they're linked.
Thanks for your feedback. Did you know that you can create infinite numbers of subactivities (down to an individual day) that will all be visualised on the timeline? The idea is that the cards' individual placements in time is of less importance and that you can follow the progress by seeing how many cards are done out of the total in the break down.
If you click on the activity you can see a lot of detail when you hover over the cards - like due date .